Electrical actuator



LA VERGNE L. SMITH 3,361,939

ELECTRICAL ACTUATOR Filed March 22, 1965 BY i rik United States Patent 3,361,939 ELECTRICAL ACTUATOR La Vergne L. Smith, Canoga Park, Calif assignor to Whittaker Corporation, Los Angeles, Calif a corporation of California Filed Mar. 22, 1965, Ser. No. 441,929 19 Claims. (Cl. 317-123) This invention relates to an electrical actuator and more particularly relates to an electrical system for initially actuating magnetic devices very rapidly but which requires only low level holding power.

' It is' desirable in tractive magnetic devices such as torque motors, solenoids, etc, to combine the characteristics of rapid initial actuation with low steady state or holding power consumption. These characteristics are essentially conflicting in nature because rapid actuation requires a low inductance and consequently a low impedance circuit while lower power consumption requires a such a system having a plurality of coil elements and related circuitry for separating its dynamic and static functions.

It is another object of the present invention to provide such a system which is capable of bilaterial actuation, i.e., which electrically actuates the device on receipt of a control signal and electrically de-actuates it upon 'termination of the control signal.

These and other objects and advantages of the present invention will become more apparent upon reference to the accompanying description and drawings in which:

FIGURE 1 is a schematic diagram of a first embodiment of the present invention;

FIGURE 2 is a schematic diagram of a second embodiment of the present invention;

FIGURE 3 is a schematic diagram of a third embodiment of the present invention;

FIGURE 4' is a schematic diagram of a fourth embodiment of the present invention;

FIGURE 5 is a schematic diagram of a fifth embodiment of the present invention;

FIGURE 6 is a schematic diagram of a sixth embodiment of the present invention; and

FIGURE 7 is a schematic diagram of a seventh embodiment of the present invention.

Turning now to the first embodiment of the present invention, FIGURE 1 shows a pair of parallel connected coils 12 and 13, the parallel combination having one side coupled to the negative terminal of a battery or other suitable electricalpower supply 14 and the other side 'coupled to the contact arm 15 of a single pole double throw switch 16. One stationary contact 17 of the switch 16 is connected to the positive terminal of the battery 14 while the other stationary contact 18 of the switch 16 is connected to the negative terminal of the battery 14. It should be understood that while a mechanic-a1 switch is illustrated, any electrical or electromechanical switch may also be used. A capacitor 19 is coupled in the circuit of the coil 12.

The coils 12 and 13 represent the driving coils of the tractive magnetic device, which as mentioned may be a solenoid or a torque motor. The coil 12 has relatively few turns of wire of relatively large size and thus has a low resistance to electrical current and a low inductance resulting in a low impedance to changing electrical current values. Only a relatively small electrical potential opposing the signal current is induced in this coil by the effect of changing magnetic flux, that is, counter-electromotive force.

The coil 13 has a relatively large number of turns of wire of a relatively small size. This coil therefore provides a high resistance to electrical current which permits the unit to remain energized at a very low power input level. This winding, however, has a relatively high inductance and consequently a high impedance to changing electrical current values. The counter-electromotive force developed in this coil by changing magnetic flux will be relatively high, which renders this coil relatively ineffective under dynamic conditions.

In operation, when the contact arm 15 of the switch 16 is engaged with the fixed contact 17, a large current flows through the Winding 12 causing the magnetic device to be actuated very rapidly. The current through the coil 12 also charges the capacitor 19. When the voltage across the capacitor 19 reaches the value of the voltage of the battery 14, current will no longer flow through the coil 12 and it is rendered inoperative for steady state operation. While the capacitor 19 charges the current through the coil 13 has built up to a value sufficient to maintain the magnetic device in the actuated condition.

When the magnetic device is to be de-actuated, the contact arm 15 of the switch 16 is moved into engagement with the contact 18. The coil 12 is now connected in a short circuit with the capacitor 19 and the latter discharges through the coil 12 in a direction opposite to the original current flow.

If the magnetic device is bipolar, such as a permanent magnet torque motor, the magnetic field created by this current in the coil 12 will exert a force on the actuated member which is consequently driven to the closed or oif position. The circuit is thus bilateral, that is, when turned on it exerts a force which actuates the magnetic device and when turned off it exerts a force of opposite polarity to de-actuate the device. In the case of a solenoid, the reverse current flow serves only to break down the magnetic flux Which is holding the unit open and provides no reverse actuation. A similar valuable purpose is served, however, as in most devices of this type the electrical time constant is greater than the mechanical time constant.

Turning now to FIGURE 2, a second embodiment of the present invention is illustrated. In this figure, a single coil 22 having a tap 23 serves the same function as the coils 12 and 13 of FIGURE 1. The upper section or coil element 22a of the coil has considerably fewer turns than the lower section or coil element 22b. The lower end of the coil 22 is connected to the negative terminal of battery 24- while the upper end of the coil 22 is connected to the contact arm 25 of a single pole double throw switch 26. One of the stationary contacts 27 of the switch 26 is connected to the positive terminal of the battery 24 while the other stationary contact 28 is connected to its negative terminal. A capacitor 29 is connected in parallel with the lower portion 22b of the coil 22.

The operation of the circuit of FIGURE 2 is similar to that of FIGURE 1. When the contact arm 25 of the switch 26 is moved to the on position, a relatively high level of current flows through the upper section 22a of the coil and the capacitor 29. As the capacitor charges the current flowing through section 22b increases until at full charge, all the current flows through the entire coil. In effect then, the series connected coil section 22a and capacitor 29 are connected in parallel with the entire coil 22 in the same manner as the coil 12 and capacitor 19 are connected in parellel with the coil 13 in FIG- URE l. Coil section 22:: serves to perform the dynamic function as does the coil 12 while the entire coil 22 serves to perform the static or holding function of the coil 13. The recitation of first and second inductive means or coil elements connected in parallel as used in the appended claims is therefore intended to embrace both of these arrangements.

In the embodiments of FIGURES 1 and 2, switching the switch to the off position results in the coil elements that control the dynamic operation of the device producing a force which drives a bipolar movable member to its off position because of the discharge of the capacitor. In both of these embodiments the coil element that controls the static function is also short circuited in the off condition and therefore the current induced in this coil as a result of the collapsing magnetic field has a subtractive effect on the closing force developed by the discharge of the capacitor through the dynamic coil. While this is acceptable for some types of operations it is generally undesirable. Circuits which avoid this undesirable feature are shown in FIGURES 3 and 4.

Turning now to FIGURE 3, each of coils 32 and 33 has one end connected to the negative terminal of a battery 34. The other end of the coil 32 is connected through a capacitor 35 to the contact arm 36 of a switch 37. A first stationary contact 38 of the switch 37 is connected to the positive terminal of the battery 34 while the other stationary contact 39 is connected to the negative terminal of the battery 34. The other end of the coil 33 is connected to the contact arm 40 of a switch 41 having a single stationary contact 42 connected to the positive terminal of the battery 34. The contact arms 36 and 40 are mechanically ganged.

The operation of the embodiment of FIGURE 3 is similar to that of FIGURE 1 with the exception that when the ganged arms 36 and 4t) of the switches 37 and 41 are thrown to the off position, the coil 33 will be open circuited and thus will not effect the action of the capacitor 35 discharging through the coil 32.

The embodiment of FIGURE 4 is similar to that of FIGURE 3 (and the corresponding elements are therefore given the same reference numerals) with the exception that the switch 41 is provided with a second stationary contact 43 which is connected by a conductor 44 to the junction of the coil 32 and the capacitor 35. When the contact arms 36 and 40 of the switches 37 and 41 are thrown to the off position, the capacitor 35 will discharge through the coil 32 in the same manner as explained previously. In addition, the current induced in the coil 33 is added to the current from capacitor 35 and positively contributes to the mechanical deenergization of the unit.

FIGURE shows a more complex embodiment of the present invention which is suitable for obtaining very high response rates and very low steady state current values. This is accomplished by having a plurality of dynamic coils 52, 53, and 54 with corresponding capacitors 55, 56, and 57 connected in parallel with a steady state coil 58. The parallel combination has one side connected to the contact arm 59 of a single pole double throw switch 60 having a first stationary contact 61 connected to the positive terminal of a battery 62 and a second stationary contact 63 connected to the negative terminal of the battery 62. The other side of the parallel combination is also connected to the negative terminal of the battery :62.

Each of the coil-capacitor combinations has an increasing time constant. For example, the coil-capacitor combination 52, 55 may have a very short time constant capable of actuating the unit extremely rapidly. Coilcapacitor combination 53, 56 may have a slightly longer time constant to render more lasting the initial pulse. Coilcapacitor combination 54, 57 may have an even longer 4 time constant to further increase the actuating pulse length. The various combinations combine to introduce a sutficient time constant into the dynamic section of the actuator to permit the coil 58 to attain a sufficiently high current value to maintain the actuator in its open or actuated condition.

The embodiment of FIGURE 6 is similar to that shown in FIGURE 5 but uses a single coil 66 having taps 67 and 68 in place of the plural coils 52, 53 and 54 of FIGURE 5. In this respect, FIGURE 6 is related to FIGURE 5 in the same manner that FIGURE 2 is related to FIG- URE l and its operation is basically the same as that of the embodiment shown in FIGURE 2. It should be understood that the embodiments of FIGURES 2, 5 and 6 may be modified in the manner shown in FIGURES 3 or 4 t obtain improved de-actuation.

FIGURE 7 shows an embodiment of the invention wherein the dynamic coil 70 is isolated from the main circuit by a transformer 71. The primary winding 72 of the transformer 71 is connected in series with the steady state coil 73 which is shunted by a capacitor 74. When the switch 75 is thrown to the on condition, a pulse of relatively high magnitude passes through the primary winding 72 and charges the capacitor 74.

This current pulse is sensed by the secondary 77 of the transformer 71 and passed to the coil 70 and rapidly actuates the device. The transformer 71, being incapable of inducing any current without a change in current value, renders coil 70 inoperative for steady state conditions. As the charge on the capacitor 74 increases, the current through the coil 73 also increases until the capacitor is completely charged and the current flowing through the coil 73 is sufiicient to maintain the device in the actuated condition.

As can be seen, each of the coil-capacitor combinations of the present invention also acts as an anticipator. This is particularly useful if the system is used as a proportional bilateral actuator where the system is calibrated to the steady state coil. The coil-capacitor combination provides a lead network responsive to changes in DC current level to anticipate changes in signal level or polarity.

The invention may be embodied in other specific forms not departing from the spirit or central characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

I claim:

1. An actuating system comprising first inductive means, second inductive means, a capacitor, a source of electrical power, a discharge circuit, and switch means operable in one condition to couple said first inductive means and said capacitor to said power source whereby said capacitor is charged and a current flows in said first inductive means, the magnitude of said current decreasing as said capacitor charges and to couple said second inductive means to said power source and to said capacitor whereby current flows through said second inductive means, the magnitude of said current increasing as said capacitor charges, and operable in another condition to couple said capacitor and said first inductive means to said discharge circuit whereby said capacitor discharges and a current flows in said first inductive means.

2. An actuating system comprising first inductive means, second inductive means, a capacitor, a source of electrical power, means coupling said capacitor and said first inductive means in a series circuit, means coupling said second inductive means in parallel with said series circuit, a discharge circuit and switch means operable in one condition to couple said parallel combination to said source whereby said capacitor is charged and a current flows in said first inductive means, the magnitude of said current decreasing as said capacitor charges, and a further current flows through said second inductive means, the magnitude of said further current increasing as said capacitor charges, and operable in another condition to couple said capacitor and said first inductive means to said discharge circuit whereby said capacitor discharges and a current flows in said first inductive means.

3. An actuation system comprising first inductive means, second inductive means, said first inductive means being a portion of said second inductive means, a capacitor, a source of electrical power, means coupling said capacitor in series with said first inductive means and in parallel with the remaining poition of said second inductive means, a discharge circuit, and switch means operable in one condition to couple said first inductive means and said capacitor to said power source whereby said capacitor is charged and a current fiows in said first inductive means, the magnitude of said current decreasing as said capacitor charges, and a further current flows through said second inductive means, the magnitude of said further current increasing as said capacitor charges, and operable in another condition to couple said capacitor and said first inductive means to said discharge circuit whereby said capacitor discharges and a current flows in said first inductive means.

4. An actuating system comprising first inductive means, second inductive means, a capacitor, a source of electrical power, means coupling said first inductive means and said capacitor in a series circuit, means coupling said series circuit in parallel with said second inductive means, a discharge circuit, and switch means operable in one condition to couple said parallel combination to said power source whereby said capacitor is charged and a first current flows in said first inductive means, the magnitude of said first current decreasing as said capacitor charges, and a second current flows through said second inductive means, the magnitude of said second current increasing as said capacitor charges, and operable in another condition to couple said capacitor and said first inductive means to said discharge circuit and said second inductive means to an open circuit whereby said capacitor discharges and a current flows in said first inductive means.

5. An actuating system comprising first inductive means, second inductive means, a capacitor, a source of electrical power, means coupling said capacitor and said first inductive means in a series circuit, means coupling said series circuit in parallel with said second inductive means, a discharge circuit, and switch means operable in one condition to couple said parallel combination to said power source whereby said capacitor is charged and a first current flows in said first inductive means, the magnitude of said first current decreasing as said capacitor charges, and a second current fiows in said second inductive means, the magnitude of said second current increasing as said capacitor charges, and operable in another condition to couple said capacitor, said first inductive means and said second inductive means to said discharge circuit whereby said capacitor and said second inductive means discharge and a current flows in said first inductive means.

6. An actuating system comprising a plurality of inductive means, a plurality of capacitors, each of said capacitors being coupled in a series circuit with one of said inductive means, a further inductive means, a source of electrical power, a discharge circuit, means coupling said further inductive means in parallel with each of said series circuits, and switch means operable in one condition to couple said parallel combination to said power source whereby said capacitors are charged and currents flow in each of said currents decreasing as said capacitors charge, and a further current flows through said further inductive means, the magnitude of said current increasing as said capacitors charge, and operable in another condition to couple said series circuits to said discharge circuit whereby said capacitors discharge and currents flow in said plurality of inductive means.

7. The system of claim 6 wherein each of said series circuits has a different time constant.

8. An actuating system comprising a plurality of inductive means, each of said means being a portion of a single coil, a plurality of capacitors, each of said capacitors being coupled in a series circuit with one of said inductive means, a further inductive means, means coupling said further inductive means in parallel with each of said series circuits, a source of electrical power, a discharge circuit, and switch means operable in one condition to couple said parallel combination to said power source whereby said capacitors are charged and currents flow in said plurality of inductive means, the magnitude of said currents decreasing as said capacitors charge, and a current flows through said further inductive means, the magnitude of said current increasing as said capacitors charge, and operable in another condition to couple said series circuits to said discharge circuit whereby said capacitors discharge and a current flows in said plurality of inductive means.

9. The system of claim 8 wherein each of said series circuits has a different time constant.

10. An actuating system comprising a first inductive means, second inductive means, a capacitor, means coupling said capacitor and said second inductive means in parallel, means inductively coupling said first inductive means with said parallel combination, a source of electrical power, a discharge circuit, and switch means operable in one condition to couple said parallel combination and said inductively coupling means to said power source whereby said capacitor is charged and a current flows in said first inductive means, the magnitude of said current decreasing as said capacitor charges, and a current flows through said second inductive means, the magnitude of said current increasing as said capacitor charges, and operable in another condition to couple said capacitor and said inductively coupling means to said discharge circuit whereby said capacitor discharges and a current flows in said first inductive means.

11. An actuating system comprising first and second inductive means, storage means connected in series with said first inductive means, means connecting said second inductive means in parallel with said series combination, and means for selectively supplying electrical power to said parallel connection or short circuiting said series combination.

12. An actuating system comprising first and second inductive means, a capacitor connected in series with said first inductive means, means connecting said second inductive means in parallel with said series combination, means for supplying electrical power, means for short circuiting said series combination, and switch means for selectively connecting said power supplying means to said parallel connection or said short circuit means to said series combination.

13. An actuating system comprising a first coil, a second coil, a capacitor, means connecting said first coil and said capacitor in a series circuit, means connecting 0 said second coil in parallel with said series circuit, means for supplying electrical power, and switch means selectively operable to connect said power supplying means to said parallel combination or to short circuit said parallel combination.

14. An actuating system comprising a coil having a tap thereon dividing said coil into two portions, a capacitor, means connecting said capacitor in series with one portion of said coil and in parallel with the other portion thereof, means for supplying electrical power, and switch means selectively operable to connect said power supplying means to said coil or to short circuit said coil.

15. An actuating system comprising a first coil, a second coil, a capacitor, means connecting said first coil and said capacitor in a series circuit, means for connecting said second coil in parallel with said series circuit, means for supplying electrical power, and switch means selectively operable to connect said power supplying means to said parallel combination or to short circuit said series circuit and open circuit said second coil.

16. An actuating system comprising a first coil, a second coil, a capacitor, means connecting said first coil and said capacitor in a series circuit, means for connecting said second coil in parallel with said series circuit, means for supplying electrical power, means for connecting said second coil in parallel with said capacitor, and switch means selectively operable to connect said power supplying means to said series circuit and said second coil in parallel with said series circuit, or to short circuit said series circuit and connect said second coil in parallel with said capacitor.

17. An actuating system comprising a plurality of coils, a plurality of capacitors, a further coil, means connecting each of said plurality of coils with one of said capacitors in a series circuit, means connecting said further coil in parallel with said series circuits, means for supplying electrical power, and switch means selectively operable to connect said power supplying means to said parallel combination or to short circuit said parallel combination.

18. An actuating system comprising a coil having a lurality of taps dividing it into a plurality of portions, a plurality of capacitors, a second coil, means connecting each of said plurality of capacitors and one of said coil portions in a series circuit, means connecting said second coil in parallel with said-series circuits, means for supplying electrical power, and switch means selectively operable to connect said power supplying means to said parallel connection or to short circuit said parallel connection.

19. An actuating system comprising a first coil, a second coil, a capacitor, a transformer having primary and secondary windings, means connecting said second coil and said capacitor in parallel, means for serially connecting the primary of said transformer and said parallel combination, means for serially connecting the secondary of said transformer and said first coil, and switch means selectively operable to connect said power supplying means to said primary winding and said parallel combination or to short circuit said primary winding and said parallel combination.

References Cited UNITED STATES PATENTS 306,225 10/1884 Cummings 317-155 1,588,186 6/1926 Hartley 317-123 1,785,819 12/1930 Silent 323-50 2,483,408 10/1949 Garber 317-155 X 2,898,524 8/1959 Stamberger 317-123 2,925,538 2/1960 Rasmusen 317-123 2,928,999 3/1960 Vinding 317-123 3,022,449 2/1962 Hyink 317-123 3,054,026 9/1962 Lovell 317-123 3,099,756 7/1963 Penfold et al. 317-151 X 3,149,244 9/1964 Barnes et al. 307-104 LEE T. HIX, Primary Examiner. 

11. AN ACTUATING SYSTEM COMPRISING FIRST AND SECOND INDUCTIVE MEANS, STORAGE MEANS CONNECTED IN SERIES WITH SAID FIRST INDUCTIVE MEANS, MEANS CONNECTING SAID SECOND INDUCTIVE MEANS IN PARALLEL WITH SAID SERIES COMBINATION, AND MEANS FOR SELECTIVELY SUPPLYING ELECTRICAL POWER TO COMBINATION. 